The present invention relates, in general, to a self-balancing device for a rotating machine part.
Machine parts normally have to a varying degree an unbalance which leads to noticeable effects, when the machine part rotates. For example, an unbalanced drum of a washer results in a creeping of the washer during the spinning stage. Other examples include hand machine tools, e.g. Hand grinders, which are caused to vibrate through imbalance of rotating parts. In a worst case scenario, such vibrations may result in bodily harm of the user.
Typically, such unbalance problems have been corrected heretofore by using compensating masses which move along a circular track. When arranged upon a shaft in proximity of an unbalance, the compensating masses tend to shift automatically to a position which is in opposition to the unbalance. In this way, a counterweight is formed for compensating the unbalance.
Self-balancing devices of this type are disclosed, for example, in German Pat. Nos. DE 919 076, DE 25 48 433, DE 27 11 561 and DE 35 09 089. Another example is disclosed in U.S. Pat. No. 4,075,909 which describes an automatic shaft balancer having a compensation ring which has an interior space for receiving balls and is made by a shaping process without material removal. The compensation ring of this type is complex in structure and requires many individual parts. As a consequence, manufacture and assembly is cumbersome and difficult, and sealing problems are encountered, when the interior space is filled with a damping fluid, because of the many existing partition gaps.
It would therefore be desirable and advantageous to provide an improved self-balancing device which obviates prior art shortcomings and which is easy to make while still reliable and fluid-tight in operation.
According to one aspect of the present invention, a self-balancing device for a rotating machine part, includes an unbalance compensation disk made through a non-cutting process and surrounding a rotation axis of a rotating machine element; and a plurality of compensating masses freely movable in the interior space and automatically assuming a position to compensate an unbalance of the machine element, wherein the compensation disk includes a first half shell and a second half shell having two axial partition planes spaced from one another in a radial direction, wherein the first and second half shells are non-detachable connected to one another.
Unlike prior art devices, the compensation disk of a self-balancing device according to the present invention includes two half shells which can be made in a simple manner in any desired shape or form through a non-cutting process and joined together. As only two partition planes exist, in applications, when damping fluid is used in the interior space of the compensation disk, the problem of leakage is no longer an issue and can easily be resolved.
According to another feature of the present invention, the first half shell has a first sleeve portion mounted to a shaft of the machine part, a second sleeve portion connected to one end of the first sleeve portion via a stepped offset and terminating in a radially extending disk-shaped ring which ends in a third sleeve portion.
According to another feature of the present invention, the second half shell has a first sleeve portion terminating in a first radially extending disk-shaped ring which ends in a slanted transition extending with respect to the rotation axis at an angle of  less than 90xc2x0 and terminating in a second radially extending disk-shaped ring which in turn is connected to a second sleeve portion.
Suitably, the first half shell may be subjected to a hardening process so as to reduce wear on the first half shell during travel of the compensating masses.
According to another feature of the present invention, the first and second half shells are interconnected by a flanged collar.
According to another feature of the present invention, the first sleeve portion of the second half shell embraces the first sleeve portion of the first half shell, and the second sleeve portion of the second half shell embraces the third sleeve portion of the first half shell.
When using damping fluid in the interior space of the compensation disk, it is suitable to dispose a seal arrangement between the first and second half shells. Suitably, a first sealing ring is disposed between the third sleeve portion of the first half shell and the second sleeve portion of the second half shell, and a second sealing ring is disposed between the first sleeve portion of the first half shell and the first sleeve portion of the second half shell. The third sleeve portion of the first half shell may be formed with a circumferential groove for receiving the second sealing ring, thereby preventing an escape of the second sealing ring during installation.
According to another feature of the present invention, the first and second half shells may be received by a massive intermediate ring. This intermediate ring may be used, optionally, to bridge installation space.
According to another feature of the present invention, the interior space of the compensation space is configured for receiving a liquid damping fluid, and the compensating masses may be configured as rolling bodies, such as ball members.